JPS62162911A - Measuring instrument - Google Patents

Abstract

PURPOSE:To easily and accurately determine the distance to the objective surface by forming an optical system for projection and photodetection on the same plane and monitoring, etc., reflected light from the object to be measured at the time of scanning by high-frequency modulated beams by a photodetecting element of a minute photodetection area. CONSTITUTION:Laser light which is high-frequency modulated by a laser 21, etc., and has little influence by the external light is made the laser beams with a laser condenser lens 23 on the same plane as a photodetecting lens 26 for photodetection and scans the objective surface 25-1, etc., to be measured via a rocking mirror 24. Then, the timing when a photodetection level of the photodetecting element 27 which is made a point where a bright point of the optical beams generating on the surface 25-1, etc., cross a photodetection axis of the photodetecting element 27 of the minute photodetection area is made maximum is determined. The distances to the surface 25-1, etc., are calculated from an angle of rocking of a mirror 24 in the timing. The distance to the objective surface is easily and accurately determined without being influenced by the external light by this constitution without necessitating a complicated linear circuit process. Further, the distance to the objective surface can be similarly determined even by detecting the timing when photodetecting outputs of two photodetecting of the minute photodetection area are made equal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a measuring device that uses laser light or the like to scan a surface to be measured with an original beam to determine the distance to a point on the surface.

(Prior Art) In a conventional measuring device of this type, as shown in the figure, a measuring head l includes a laser light source //, a converging lens 12, and a light receiving lens 1.
3. Equipped with a linear position sensor lμ, when the position of the surface to be measured is changes as 73m + /j b *ljC, the imaging position on the linear sensor /≠ becomes /6JI
I /Ab+ /Ac, the angles θa, θb, θcf of the light receiving lens at that time are detected, and calculation processing is performed based on the distance d (laser light source 1/ and linear position sensor l≠). That is, the laser light generated by the laser light source // is converged onto the surface to be measured /J' by the converging lens l.

The reflected light of this light spot is at a certain angle (θa,
The light is focused by the light receiving lens 13 on the light receiving axis having θb, θc) and is imaged onto the linear position sensor/≠. Measuring head l and surface to be measured l! The distance is /ja・
/jb, /jc, the imaging position on the near sensor /4 moves as shown by /6a +l, /lsc. The linear position sensor l≠ is represented as a resistor with three electrodes ■, ■, ■ as shown in FIG.

■'t8: The flow ratio changes. This change in current is detected and addition/subtraction processing is performed between the two to detect the imaging position on the "r + J near sensor, determine the angle between the light emitting axis and the light receiving axis, and calculate the distance on the surface to be measured.

(Problem to be solved by the invention) Although this measurement method has the advantage of not having any moving parts for measurement, it requires linear processing for detecting minute flows and complex arithmetic processing, and requires external If additional disturbance light is incident, t
There was a drawback that the flow ratio changed. In addition, a method of modulating the laser beam is also used to remove the shadow #.
Due to the frequency characteristics of the linear position sensor, it may not be possible to select a sufficiently high frequency that will not be affected by ambient light.

(Means for Solving the Problems) The present invention has been made in view of the above points, and its object is to form an optical system consisting of a light projector and a light receiver on the same plane, and to The laser light source scans the surface to be measured by reciprocating a laser beam whose light intensity is modulated at a constant frequency within a certain angle, and the edge of the laser beam generated on the surface to be measured receives minute light. The timing at which the light receiving output of the above-mentioned light receiver reaches its maximum level at the point where it intersects with the light receiving axis formed by the light receiving axis with the area of The value is detected, the angle of the laser beam from the reference line at this time is determined, and the distance to the surface to be measured is calculated from the distance between the emitter and the receiver and the detected angle. This is a characteristic measuring device. The present invention will be explained in detail below with reference to the drawings.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention,
A measurement head is composed of a laser 21, a laser drive circuit, a laser collector 3, a swinging mirror, 2≠, a condenser lens 26, and a light receiving element 27. The light emitted from the laser J/ is condensed by a focusing lens 23, and the original beam is focused onto the surface to be measured according to the rotation angle of the swinging mirror 21 rotated by the rotation axis r. Scan above. This original beam is reflected by the surface to be measured, and when it is irradiated onto the original axis of the light receiving system formed by the condenser lens 26 and the light receiving element 27, one beam of reflected light is focused and sent to the light receiving element 27. An image is formed on top of the beam to generate a received light output. In other words, the number of surfaces to be measured is 2! Mirror 2 when at distance a
7 The distance to the surface to be measured is shown in Fig. 2.The distance to the surface to be measured is shown in Figure 2. As shown, the distance between the center of the light-receiving lens 2t and the rotation center 21-/ of the swinging mirror 2μ is d, and the light-receiving axis formed by the light-receiving lens 2t and the light-receiving element 27 is arranged at right angles to the line connecting the two. For example, the surface to be measured, 2j-portion 2
j, @ 1.21-s distance ht + ht+ h
s is expressed by the following formula.

- θ1=(・・・・・・・・・・・・・・・・・・
...... (1) - θt =!・・・・・・
・・・・・・・・・・・・・・・・・・・・・ (2
) It has the advantage that it can be easily calculated from the above formula.

Now, returning to FIG. 1, the intensity of the laser 21 is modulated at high frequency by the output of the oscillator 36 via the laser drive circuit-1. The output of this oscillator 36 is simultaneously output to the counter 3.
A digital-to-analog D/A converter 31A using a D/A converter or the like converts the signal into a linear signal that changes over time. Rotate the rotation axis r of the swinging mirror 2hiro. In other words, the angle of the laser source beam reflected by the swinging mirror changes with respect to the drive current as shown in FIG. If it is set to be proportional to the count value in 33) in Figure 1, the original laser beam angle can be obtained by calculating the count value, and the distance to the surface to be measured can be determined by the method shown in Figure 2. Desired.

The output of the light receiving element 27 shown in FIG. 1 is selected via an amplifier 37 by a bandpass filter/rectifier/smoothing circuit 2 matched to the modulation frequency, converted into a DC signal, and the peak value of the DC signal is detected by a peak detection circuit. 30, the count value of the counter 3j at this point (i.e. rotation angle) is given to the arithmetic processing circuit 32 via the gate circuit 31, and the above (
1) Calculation processing shown in equations (8) is performed.

Figure ≠ shows a relationship diagram of current waveforms to explain the operation of the configuration shown in Figure 1, and (4) shows the change in the rotation angle with respect to the current (count), which oscillates at an angle from θ to θ2. move. (B) shows the output waveform of the light receiving element 27, (C) shows the output waveform of the band pass filter, (■) shows the output of the rectifier/smoothing circuit 2, [Yes]) shows the output of the peak detection circuit 30, and the solid line is the output at the rotational angle center position, and in FIG. 1, an example of how the output changes when the distance changes is shown by a dotted line.

Here, in order to obtain the above output (), the light receiving width of the light receiving element 27 is small and the focusing of the laser source is sufficiently sharp.
A photodiode or the like having a light receiving width on the order of μm is suitable. This can be said to be suitable for receiving high frequency modulated light without affecting disturbance light. Next, FIG. 5 is a block diagram showing the configuration of another embodiment, and FIG. 6 is a diagram for explaining its main operation. In this other embodiment, two sets of light receiving elements of the measurement head 2' are provided, and the light receiving elements 27-/ and 27-2 are arranged on both sides of the light receiving axis with a slight distance apart as shown in FIG.

Each light-receiving element is converted into a DC level signal via amplifiers 37-/, 37-2, bandpass filter/rectifier/smoothing circuit Cotter/, and 2-turco, respectively. Changes in these two outputs according to the rotational movement of the laser source beam will be explained with reference to FIG.

In other words, one of them has (
As shown in A), the current is maximum when the current is I, and the other outputs (0)
is the maximum when the rotation angle changes from (4), and the two output levels tA and t are
It becomes equal to c. If there is a single light-receiving element on the light-receiving axis as shown in Figure 1, the output will be as shown in Figure 7 ω),
The same effect can be obtained by performing this peak detection and by performing level coincidence detection of (A) and (B) by the comparison circuit 30 shown in FIG. In this embodiment, the light reception accuracy is more precise than in the case of FIG. 1, and distances can be reliably measured even on a complex target surface.

(Effects of the Invention) As explained above, according to the present invention, by using a microscopic light receiving element suitable for receiving high frequency modulated light that does not require complicated IJ near circuit processing and has no influence on disturbance light, Distance can be easily measured by the output level monitoring process, and an economical measuring device can be realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
Figure 3 is a diagram explaining the measurement principle, Figure 3 is a diagram explaining the correspondence between mirror drive current and original beam angle, Figure 5 is a diagram explaining rotation angle detection, Figure 5 is a block diagram showing another embodiment. 6 is a diagram explaining the arrangement of the light receiving element, FIG. 7 is a diagram explaining the detection operation, FIG. R is a diagram explaining the conventional measurement method, and FIG. This is an equivalent circuit of a linear position sensor. λ...Measuring head, 21...Laser, 23...v
-The original focusing lens, 2μ...Swinging mirror 1.26...
・Condensing lens Core... Light receiving element, λ bandpass filter/rectification smoothing circuit, 30... Peak detection circuit, 32... Arithmetic processing circuit, 33... Mirror drive circuit, 31A. ...D/A conversion circuit, 3j...counter, 36...oscillator, 37...amplifier.・J5.・ #l zurei)! 'I foot-to-foot image plane 2 Figure charge - I O+1 (current) * 4 Figure ￥ 5 Gu Hei 6 Figure den ) L * 7 Figure No. 6 (211 Broom 9 Concave)

Claims (1)

[Claims] An optical system consisting of a projector and a receiver is formed on the same plane, and the laser light source of the projector reciprocates within a certain angle a laser light beam that has been modulated in light intensity at a constant frequency and moves over the surface to be measured. The timing at which the light receiving output of the light receiver reaches its maximum level at the point where the bright spot of the laser beam generated on the surface to be measured intersects with the light receiving axis formed by the light receiver having a small light receiving area, or the light receiving The peak value is detected using a signal obtained through a bandpass filter/rectifier smoothing circuit that extracts only the modulated frequency component at the timing when the output levels of two light receiving elements placed at a minute distance on both sides of the axis are equal. A measuring device characterized in that the angle of the laser beam from the reference line at this time is determined, and the distance to the surface to be measured is calculated from the distance between the emitter and the receiver and the detection angle. .